Here is the full list of all 86 Ato achievements.
Beat Ato on Accessible Difficulty
Once obtained, Successfuly perform the counter ability on an enemy
Defeated Demon
Max out your magic meter
Defeated Vagrant
Perform the just-frame legendary move
Defeated Leader
Completed Throw Arena
Hit opponent 5 times while they are launched
Defeated Cross Blade
Completed Fatal Arena
Defeated Champ
Defeated Blameless
Obtain all talismans
Defeated Archer
Collect a magic bar
Defeated Tiny Warrior
Completed Armor Arena
Defeated Turtle
Collect all coins
Defeated Warden
Defeated Tempest
Defeated Geisha
Defeated Bandit
Defeated Monk
Defeated Yari
Defeated Child Statue
Defeated Shadow Jin
Completed Spin Arena
Defeated Daggerman
Destroy 50 wall crystals
Defeated Deceiver
Defeated Father Statue
Defeated Samurai
Defeated Sentinel
Warp from one gate to another
Defeated Phantom Shin
Equip a Rune
Obtain your first Rune
Defeated Twins
Defeated Ancient Warrior
Defeated Mother Statue
Destroy a blue crystal block
Defeated Acolyte
Defeated Ninja
Jump 1000 Times
Defeated Guardian
Obtain your first Coin
Defeated Jin
Parry your opponent
Obtain your first Talisman
Increase your max health
Defeated Rogue
Defeated Berserker
Defeat The Leader without killing his servants
Defeated Warden without the vision upgrade
Perform the legendary move on an enemy
Obtain all scrolls
Collect all runes
Collect EVERYTHING
Cut 50 stalks of bamboo
Beat Ato on Experienced Difficulty
Beat Ato on Bushido Difficulty
Beat the first 3 bosses on Hell Difficulty
Beat Ato on One Hit Difficulty Mode
Beat Ato without collecting a Rune
Beat Ato without obtaining a dodge ability
Beat Ato without collecting Talismans, Coins, Runes nor extra Magic
Beat Ato in 2 Hours